The present invention generally relates to a branch joint box for performing branching of a circuit through branch joint of connectors of a wiring harness, etc. for a motor vehicle and more particularly, to prevention of penetration of water into a casing of the branch joint box.
In a branch joint box used for joining a wiring harness for a motor vehicle to various electrical parts by branching, branch joint points are concentrated at one spot so as to reasonably and economically join a circuit by branching. In response to rise of densities of wires of the wiring harness, various types of branch joint boxes have been developed.
As shown in FIGS. 1 and 2, a known branch joint box includes a lower casing 1 and an upper casing 2. In the known branch joint box, when an outer surface of an outer peripheral wall 2a of the upper casing 2 is fitted into an inner surface of an outer peripheral wall 1a of the lower casing 1, a locking projection 1b formed on the inner surface of the outer peripheral wall 1a of the lower casing 1 is caused to ride over a locking projection 2b formed on the outer surface of the outer peripheral wall 2a of the upper casing 2 so as to be brought into engagement with the locking projection 2b such that the lower and upper casings 1 and 2 are locked to each other. Meanwhile, upper and lower portions of the lower and upper casings 1 and 2 locked to each other as described above are closed by upper and lower covers (not shown), respectively.
Since the branch joint box is provided in an engine compartment of the motor vehicle, countermeasures for preventing penetration of rainwater, etc. into the branch joint box and discharging the penetrated rainwater, etc. from the branch joint box are taken. As one of such countermeasures, a drainage hole 1c for discharging the penetrated rainwater, etc. from the branch joint box is formed on a bottom wall of the lower casing 1.
However, since the drainage hole 1c is formed by utilizing a recessed portion of the lower casing 1 for molding the locking projection 1b, the drainage hole 1c is disposed immediately below the locking projection 1b. Therefore, such a case may happen that rainwater, etc. flow reversely from the drainage hole 1c into a gap t between the lower and upper casing 1 and 2 as shown by the arrow a. At this time, since below the locking projection 2b of the upper casing 2, there is nothing preventing penetration of rainwater, etc. into the branch joint box as shown in FIGS. 3 and 4, the rainwater, etc. may pass by opposite sides of the locking projection 2b from below the locking projection 2b so as to penetrate into the upper casing 2, thereby resulting in immersion of a bus bar, etc. in water.